Nitride semiconductors are used in various fields such as optical devices including light emitting and light receiving devices, and high speed electronic devices including radio frequency devices.
Silicon substrates are superior in mass productivity. However, in a nitride semiconductor crystal formed on a silicon substrate, cracks and other defects are likely to occur due to the difference in lattice constant or thermal expansion coefficient. Furthermore, to achieve high performance, there is demand for a high quality crystal with few dislocations.